cancel
Showing results for 
Search instead for 
Did you mean: 

Fuel economy!!

Community Veteran
Posts: 7,149
Thanks: 51
Fixes: 2
Registered: 30-08-2007

Fuel economy!!

Ok another motoring topic...
Over a 10 mile or so stretch of the M25 I use regularly at relatively quiet times of day (yes! there are some) I have been assessing my fuel economy at different speeds. The car is a 2003 Toyota Avensis 1.8 auto.
At 65mph my trip computer shows between 43 and 45mpg (I won't bore you with the post decimal figures)
At 70mph it improves to 47 to 49mpg
At 75mpg (shusssh!) it will record anything between 54 and 56mpg
I'm not complaining about any of those figures, but do you think I can quote the 75mph figure as defence, in the interests of economy if pinched for speeding? Is it right that I should have to break the law to do my bit to save the planet?
Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.
41 REPLIES
N/A

Re: Fuel economy!!

Don't know a deal about fuel economy although I used to check my own frequently when I had a car by filling up, checking the mileage and using my calculator.
Now I have noticed that when I mostly drive the car fuel seems to go further than the other half who, like most men, does a fair amount of erratic driving!  I, like most ladies, tend to drive much better and smoother, thereby getting more miles to the gallon. 
We have an LPG conversion now and it is pretty much the same mpg as petrol - perhaps a little more.
Community Veteran
Posts: 7,149
Thanks: 51
Fixes: 2
Registered: 30-08-2007

Re: Fuel economy!!

Poppy, at the expense of upsetting other men, I've been married twice, both times to extremely good drivers, especially my first wife whom, I must say is one of the best drivers I've ever encountered.
Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.
pierre_pierre
Grafter
Posts: 19,757
Registered: 30-07-2007

Re: Fuel economy!!

I have a very good right trained foot as used do fuel ecomony test as part of my job for over 30 years.had to keep an exact constant speed over a flat horizontal mile.
But yes my little KA is far more economical cruising at 70 than shunting at 30-40 MPh
Out of touch with the Dyno test people now, but would like to see the Brake Specific Fuel consumption graphs
http://autospeed.com/cms/title_Brake-Specific-Fuel-Consumption/A_110216/article.html
nadger
Rising Star
Posts: 4,498
Thanks: 46
Registered: 13-04-2007

Re: Fuel economy!!

Quote from: poppy
We have an LPG conversion now and it is pretty much the same mpg as petrol - perhaps a little more.
Chap who brought me back from hospital a couple of times had car with lpg conversion and I was really impressed with it's performance. Certainly wouldn't have known it had conversion if hadn't been told.
pierre_pierre
Grafter
Posts: 19,757
Registered: 30-07-2007

Re: Fuel economy!!

this shows what I am after, the most econimical is around the 3500 rpm
Community Veteran
Posts: 7,149
Thanks: 51
Fixes: 2
Registered: 30-08-2007

Re: Fuel economy!!

Interesting to note I think pierre, that the lowest (poorest) figures are around the "official" 56mph figures quoted in most sales advertising.
Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.
pierre_pierre
Grafter
Posts: 19,757
Registered: 30-07-2007

Re: Fuel economy!!

that depends on your gearbox.  I have a rev counter on the display, but dont often look.  I have seen it in print recently only use the 5th gear for higher speed motorway.
N/A

Re: Fuel economy!!

Nadger - interesting that you should make that observation about the LPG conversion car that you travelled in.
When ours came back from the conversion company the first thing I noticed when I drove it was just that - i.e. it seemed livelier and quieter.
Also supposed to be better for the environment.
Lurker
Grafter
Posts: 1,867
Registered: 23-10-2008

Re: Fuel economy!!

Fuel economy these days has more to do with throttle position than engine revolutions, and its for this reason that the advice is given as you say P_P.
Foot planted in the carpet to deliver 50mph in 5th gear up an incline will deliver lower economy in most cars than foot 25% depressed in 4th gear to maintain 50mph on the same stretch of road.
I know it won't really be news to P_P (or many other readers), but many people think that if the engine is rotating more, then it will use more fuel.
Of course, if you drive a vehicle with a carburettor instead of fuel injection, all bets are off, and the 'old' logic of RPM being more directly linked applies (but remember that even in this setup, its not a direct relationship)
Community Veteran
Posts: 16,825
Thanks: 1,115
Fixes: 13
Registered: 06-11-2007

Re: Fuel economy!!

I am very concerned about how many miles I can get out of a gallon of diesel.....
some tips I have learned and used over the years....
1. remove the roof rack, when not in use.... (Causes drag, and needs extra fuel to cover same distance at same speeds)
2. remove the tool box and any other excess weight  from the boot....
3, (a bit awkward this one) (because of 4 below) ....never fill the tank for short journey travels.... (extra weight of fuel you are carrying around )
4. Fill the tank to the neck (a term described as "brimming") then go on a long journey 3-400 miles, then refill to neck.... note the mileage, and the litres, do the sums to check the mpg.
5. use the very lightest right foot and accelerate smoothly through the gears. (boy racers getting away first at the lights is not recommended !)
6. anticipate the braking ..... forward thinking for junctions, turns, roundabouts, traffic lights, pedestrian crossings,  - use gravity and wheel/road resistance to slow the vehicle.
7. climbing hills/inclines use the highest gear possible without straining the engine.
8. (my personal one) knock the car out of gear and coast down hills (not really steep hills, or dangerous bendy ones ! ! ).  (use your common sense!)  If you use a road regularly that has a long incline downhil, you can save 1 mile a day = 5 miles a week = 20 miles a month ! !)
9. switch off at traffic lights, especially if you know it is a long wait..... also use the handbrake, if you sit there with your foot on the brake, you are burning the filaments in your brake light bulbs, so will have to replace them more often. !
10. Always REVERSE into a parking space..... it is easier to get out, and an engine uses more fuel when starting from cold to reverse out of a parking space, than one driving straight out
11. If possible park the car in a shady spot, when the sun is very hot.... if you leave the car in the sun all day long, evaporation can take place in the tank.
12.... it is not the accelerator that wastes fuel.... it is the brake pedal...... think of it like this..... if you are going too fast.... you have made a mistake, and have to correct it by using the brakes. ! !  all the kinetic energy you have given the car by pressing on the accelerator to get it moving faster is lost when you use the brakes.

pierre_pierre
Grafter
Posts: 19,757
Registered: 30-07-2007

Re: Fuel economy!!

13 dont use the AC that can add 10% to fuel consumption
5 never did do enough tests, but on the Old Post Office supply tender trial, the Economy test was a 1/4 mile accel cruise stop repeated for 10 mile.  By accident I found that getting to the cruise speed of 30 as quick as possible - you had to use all gears - actually saved fuel, everbody else was using a feather on the throttle, just reaching 30 at the end of quarter
7 see James G comment above
8 I thing that is considered not being in control of a vehicle and can get you in trouble
Community Veteran
Posts: 3,486
Registered: 02-10-2008

Re: Fuel economy!!

I've heard that the more recent climate control systems are more efficient that the older air conditioning systems - is this true - do they just turn the A/C on when needed ?
What about cruise control - I presume that has a "lighter foot" than a human driver - so more fuel efficient ?
What about modern auto gear boxes such as the Ford group six speed Powershift transmission with dual-clutch technology ? - this has a claimed fuel consumption very close to a manual box - but then on the other hand would a good auto box such as this keep the car in the optimum gear and so provide better fuel consumption for the average driver ?.
jmd
Grafter
Posts: 2,933
Thanks: 2
Registered: 30-07-2007

Re: Fuel economy!!

How to save fuel - don't use the car!  Tongue
Community Veteran
Posts: 16,825
Thanks: 1,115
Fixes: 13
Registered: 06-11-2007

Re: Fuel economy!!

Another point I forgot to add to my list.... especially true with diesel engine cars..... make sure you keep to the oil change and oil filter (and air filter) change mileages.
I have a Skoda Fabia 1.9 SDI, Y reg 2001. which makes it 8 years old..... I bought the car secondhand from a garage, had a full service and mot on purchase, and kept up the service times, it had 55,000 miles on the clock was 3 years old, so I have had it for 5 years..... In the price guide book, it was rated at 65 mpg when new, my first mpg tests gave 62mpg..... it now has 132,000 on the clock, and last week I did a mpg check.  61.2 mpg over 470 miles (300 motorway and the rest just local running around ).... I have just had the clutch replaced..... t(he clutch cover was losing it`s "spring". but the plate still had a few thousand miles according to the garage works foreman)